Several postings about this on a different thread, so I thought we’d better redirect them to a new thread.
It has come up many times in the past, search porcelain.
Here are mine, done by Prairie Porcelain in Minnesota.
I used a disc sander on them before I sent them off.
Still holding up fine 6 years later.
I get compliments about them at street rod cruise nights.
A good friend just had his done by PP. they were sent back to me for misc reasons and I thought the workmanship was really good. The pieces looked to have been thoroughly cleaned and smoothed over. The coating was very uniform and not horribly thick. The non-cosmetic areas such as the face/flange and inside/runners also looked to have been nicely cleaned up and coated with something.
Taking a belt and suspenders approach we heat cycled them per the instructions that come with the SNG manifolds.